Mechanical fasteners are widely used for joining two or more components of a structural assembly. For example, mechanical fasteners are used extensively for joining the structural components of an airframe. Two-piece fasteners are used in a variety of applications including applications where tension loads in the fastener are relatively high. Such two-piece fasteners may include a bolt or a pin that is inserted into a hole and a threaded nut or swage collar that may be mechanically secured to threads or other features formed on the free end of the bolt or pin. By tightening the nut or collar against the structure, the components of the structural assembly may be clamped together.
Although two-piece fasteners generally provide relatively high clamp-up and tension load-carrying capability, two-piece fasteners suffer from several drawbacks that detract from their overall utility. For example, due to the need to fabricate, process, and store a large quantity of each component of the system that comprise two-piece fastener systems, procurement costs are relatively high. In addition, the time required for installation and assembly of two-piece fasteners in a structure is relatively high and may require separate, unique tools for the various components of the two-piece fastener configurations, which may add to production costs.
Furthermore, the need to handle two separate pieces for each two-piece fastening system adds to the complexity of installation, which may undesirably add to the overall production time considering the relatively large quantity of fasteners (e.g., tens of thousands) that may be installed in a single airframe. Even further, two-piece fasteners may be relatively heavy due to the required size or length of the mating nut or collar to sufficiently engage the threads formed on the end of the pin or bolt to provide adequate clamp-up and tension load-carrying capabilities. Due to the high volume of fasteners utilized in a single airframe, even minor savings in weight, cost, and time associated with the fasteners can results in significant savings over the number of aircraft produced during the life of a program.
As can be seen, there exists a need in the art for a fastener system having reduced complexity of installation and which may be installed in a reduced amount of time while providing strength characteristics that are at least equivalent to conventional two-piece fasteners.